1. Field of the Invention
The present invention is directed generally to computer communication networks, and in particular, to an improved communication network that provides superior quality of service (hereinafter xe2x80x9cQOSxe2x80x9d) guarantees.
2. Description of the Related Art
Quality of Service guarantees are necessary for efficient network communication, and in particular for distributed multimedia applications. The need to provide a high quality of service for continuous-media and real time applications is well recognized in the communication networking community.
Two known modes of communication within a computer communications network are circuit-switching and packet-switching. In a communications network configured for circuit-switching, a dedicated communication path between two (or more) communicating programs is established for use by the communicating programs only. A traditional telephone network is an example of a communication network that utilizes circuit-switching. Although an advantage of a communications network that uses circuit-switched connections is very reliable communication between the communicating programs, a severe drawback is that resources must be reserved for establishing and maintaining the entire link during the communication. Since the computer communication is xe2x80x9cburstyxe2x80x9d (i.e. communicating programs communicate with each other by exchanging information in bursts in which information is exchanged continuously for a small period of time followed by relatively xe2x80x9clongxe2x80x9d periods of silence), a communication network based on circuit-switching has a relatively low utilization of network resources.
In a network that employs packet switching, the two (or more) communicating programs do not have any reserved physical network resources. Instead, information originating from a sender program and destined for a receiver program is transmitted in units called xe2x80x9cpacketsxe2x80x9d. Each packet contains information that identifies the receiver program to which the packet of information is intended. And, based on the address of the receiver program, the packet will be continuously switched throughout the network until the intended receiver program is reached.
In a packet-switched network, packets of information may be forwarded to their destination by intermediate nodes using information in a packet header. The information may be a destination host address (as in IP) or a connection identifier (such as the VPI/VCI field in ATM). Packets can typically be transmitted by a sending host at any time. In some networks, e.g. ATM, packets are constrained to be transmitted using a rate-controlled approach. Each packet is routed independently by the nodes in the network. However, once the packet of information is established by the sender program, the contents of the information packet does not change and remains unchanged as it moves about the nodes of the network until it reaches its destination program.
Packet-switching networks can operate in two modes, as datagrams or as virtual circuits. In a typical datagram mode, packet headers contain (a) information identifying the address of the recipient and (b) any other information that may be needed for processing the packet at any intermediate nodes in the network. The packets of information being transmitted in a network in the datagram mode may be delivered out of order and can take any available path to the receiver in the network. In fact, in a typical situation, the transmitted packets of information are not transmitted together or reach the recipient together since there is no predefined path in which the packets of information travel. Accordingly, there is no guarantee that all the transmitted information will in fact (a) reach the recipient or (b) reach the recipient in the order in which it was transmitted. This latter problem becomes significant in the situation in which information must be received within a specified period or in a particular sequence.
The virtual circuit mode is advantageous over the datagram mode in that the header may be more simply configured since it may merely need contain only the identifier for the path on which it is transmitted in the network.
In a network that operates in a virtual circuit mode, a fixed route is selected at the beginning of the communication for all the packets originating from the receiver.
In general, packet switching better utilizes network resources than networks utilizing only circuit-switching. However, packet-switching networks do not provide the same quality of service (QOS) guarantees provided by a circuit-switching network since, by definition, there are no dedicated physical circuit connections among the communicating programs (computers).
As computer networks further evolve to support audio and video applications together with data applications, a need exists to provide increasing and more reliable quality of service guarantees. Several prior attempts have been made to incorporate networking schemes which provide satisfactory and sufficient quality of service guarantees. Invariably, all of these schemes are based on some form of virtual switching techniques. That is, the known virtual-circuit switching networks utilize resources which are reserved when the virtual circuit is established and released when the virtual circuit is destroyed. When virtual circuits are established, known admission control schemes can be used to attempt to guarantee that a certain quality of service is provided for the establishment of node interconnections before the virtual circuit is established.
However, computer networks that only utilize virtual circuits are deficient in the following respects. For example, establishing a virtual circuit typically takes a relatively long time and does not provide efficient and sufficient quality of service guarantees in communications that last a relatively short amount of time.
Therefore, a network architecture for use in a communication network that provides for greater QOS guarantees than heretofore achieved and which overcomes the aforementioned deficiencies is desired.
Generally speaking a communications network for transmitting an information packet between nodes of the network is provided. The network preferably comprises at least a source node and a destination node and an information cluster transmittable between the source node and the destination node and for having attached thereto an information packet. The information packet is attachable to the information cluster at the source node when the information cluster is at the source node and detachable from the information cluster at the destination node when the information cluster is at the destination node.
An information cluster will travel about the network along a predetermined path between preselected nodes within the network. Information packets originating at a node among the selected nodes along the predetermined path can be attached to the information cluster when the information cluster arrives at the particular node at which the information packet is waiting. Similarly, the information packet can get off the information cluster at any node of the selected nodes when the information cluster reaches its destination node.
The entire network, in addition to carrying information packets, will preferably carry a plurality of information clusters, although a network with as few as one information cluster is contemplated by the present invention. The information clusters are pre-scheduled and travel between selected nodes at preferably regular intervals. Because of the regularity and predictability of the information clusters, a particular node in the network will know in advance when an information cluster will arrive at that particular node. In this way increased and more reliable QOS guarantees can be provided to the information packets in the network which are attached to the information cluster.
In addition to providing information clusters as disclosed herein, the network may contain additional known networking schemes as described above. In fact, it is contemplated by the present invention that if the information packet cannot be attached to an information cluster because there is no available space thereon or there is no scheduled information cluster scheduled to go to the node to which the information packet must be transmitted within a specified time-period, a different (known) switching scheme such as packet switching would be used for the transmission of the information packet.
Information clusters may be thought of as a combination of the STM (synchronous Transfer Mode) and the ATM (Asynchronous Transfer Mode) approach to handling packets. That is, in STM, packets can only be sent at fixed times, while in ATM packets can be transmitted at any time. In a communication network constructed with the present invention, if an information packet is to be transmitted via an information cluster, the information packet must wait for a prescheduled information cluster to arrive at the node at which the information packet is waiting but may occupy any available space on the information cluster.
When an information packet has to be transmitted between two nodes, the origination node (the node at which the information packet originates) preferably determines on which information cluster the information packet will be carried. The originating node also preferably reserves space for the information packet on the arriving information cluster. Thereafter, the information packet waits for the information cluster to arrive at the node before the information packet can be put on the information cluster.
As the information cluster arrives at each selected node, the node at which the information cluster is located examines if there are any information packets on the information cluster that identifies that particular node as a destination node. If such node has been identified as a destination node for a particular information packet, the information packet destined for that node is removed from the information cluster.
An information packet that needs performance guarantees (QOS requirements) must be able to reserve space on the information cluster in advance so that it is guaranteed transmission by the information cluster. An information packet having a low priority status can also get on an information cluster if there is available space but may get bumped off and placed in a buffer (or the like) if there is an information packet with greater QOS requirements.
Each node within the network knows the arrival and departure times of the information clusters traveling between nodes. Each node also knows the capacity of each arriving information cluster. Therefore, a particular node can easily determine whether it has enough resources to meet the requirements of all the information clusters at any particular node. Any one of several known admission control tests used in conjunction with known schemes can be used for this purpose. In order to provide QOS guarantees in the network, each node has to allocate enough space for the contemplated number of information clusters that may arrive at the node and decide on an upper bound on the delay in processing packets in the cluster. Each information cluster therefore preferably has a designated processing time at each node.
An information packet needing QOS guarantees must be scheduled on an information cluster and therefore must reserve space thereon. Once the information packet has reserved the space, it is guaranteed to have a QOS similar to that of the information cluster on which it will travel. However, if a particular information packet arrives at a particular node or originates at the particular node after the information cluster has passed through that node, the information packet may need to be transmitted by conventional methods such as packet switching.
For example, if the information packet cannot be transmitted between two nodes via a information cluster, a virtual circuit between the two nodes can be established for such transmission.
Lastly, individual or a plurality of information packets can be attached to an information cluster at any point along the network routes and can be detached therefrom at any desired node along the route. In accordance with the invention, information clusters will operate with guaranteed quality of service parameters, and, therefore, information packets requiring a certain quality of service guarantee need to be attached to the appropriate information cluster.
Accordingly, it is an object of the invention to provide an improved communication network architecture that can be utilized on the internet and in corporate intranets, and is particularly useful during browsing thereon, such as the world wide web.
Another object of the present invention is to provide transmission of information in a network that can be more reliably assured that congestion and other problems on the network are not encountered.
Still another object of the present invention is to provide a communications network that increases the reliability that information will be accurately and reliably transmitted between computers or the like.
A further object of the present invention is to provide a communications network that will satisfy quality of service performance requirements.
Still another object of the present invention is to provide a connection-less network which will result in a substantial reduction in network resources.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, the apparatus embodying features of construction, combination of elements, and arrangement of parts which are adapted to effect such steps and the article which possesses the characteristics properties and relation of elements, all as exemplified in the detailed disclosure hereinafter set forth, and the scope of the invention will be indicated in the claims.